The present invention generally relates to communications systems and, more particularly, to wireless systems, e.g., terrestrial broadcast, cellular, Wireless-Fidelity (Wi-Fi), satellite, etc.
Recently, the Digital Multimedia Broadcasting for Terrestrial Television (DMB-T) Standard was published for Digital Television (DTV) broadcasting in China (“Framing Structure, Channel Coding and Modulation for Digital Television Terrestrial Broadcasting System,” NSPRC, August 2007). The DMB-T standard specifies that a receiver support a single carrier (SC) modulation mode and a orthogonal frequency division multiplexing (OFDM) modulation mode (a multicarrier mode). For the single carrier mode, Quadrature Amplitude Modulated (QAM) symbols are transmitted directly. For the multicarrier mode, QAM symbols are modulated by an inverse DFT (discrete Fourier transform) operation. The DMB-T signal comprises a hierarchical frame structure with signal frames providing the basic building block. A signal frame 10 is shown in FIG. 1. Signal frame 10 comprises a frame header 11 and a frame body 12. Frame header 11 has three frame header modes of different lengths. As can be observed from FIG. 1, these lengths are 420, 595 or 945 symbols. Frame body 12 conveys 3780 symbols, of which 36 symbols are system information and 3744 symbols are data. In a DMB-T system, a time-domain synchronous OFDM (TDS-OFDM) technique has been adopted. As such, the frame headers include pseudonoise (PN) sequences that serve as pilot signals and which are also used as guard intervals instead of cyclic prefixes as found in typical OFDM transmission such as used in DVB-T (Terrestrial) (e.g., see ETSI EN 300 744 V1.4.1 (2001-01), Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television) used in Europe.